Don't Use Numbers
I recently read a book in which the narrator described another character as "hulking" and "imposing" and "scarily intimidating". The character in question was also specifically described as 6'2" and 210 lbs.
That's tall, sure. But it's also pretty slim, especially considering this character was a professional athlete and therefore very fit, so that 210 would have been almost entirely muscle, and that weight, combined with low body fat, would cut a pretty slim figure.
Could someone have found him intimidating? Sure! But probably not because of his size. His demeanor, his personality, his behavior, all those things could be intimidating. If you, the reader, is 5'3" and 98 lbs, then this character probably does feel huge to you. But my oldest kid is bigger than this, in both height and weight, and so those numbers don't sound scary to me in the slightest. And I got bumped out of the story because of it.
Anytime you use a specific number to describe your character, either height or weight, your audience will automatically compare that number to themselves or to people they know well. That comparison might come out the way you want it to, but more likely it will not.
Luckily, this is a very easy problem to avoid, and the old adage of "show, don't tell" helps a lot here.
In DUMPLIN', Julie Murphy never says how much Willowdean weighs. Never says how tall she is or what size dress she wears. What she does say, however, is that Willowdean must wear a dress to work because the uniform company does not make pants in her size.
That conveys fatness in a way that numbers never could, and it conveys the struggles of being a fat girl in a fat-phobic society. One quick sentence and she conveyed everything she needed to convey about this character's size while also conveying some societal problems and she manages to do it without calling out the reader in any way. The problem here is with the uniform company, not Willowdean's body. The problem is with societal expectations, not with the reader.
Show us how your character's body moves through the world, don't tell us what size they wear. Some examples:
A hero whose muscles strain against the seams of his shirt.
A teen girl who shops in the kids' department because her curves haven't come in.
A teen girl who must fend off advances of adult men because she's tall and extra curvy, appearing much older than she actually is.
A mother who wears athleisure every day because jeans cut into her soft belly.
A villain who has to duck everytime he walks through a door.
A junior high student who struggles with the dress code because she's too tall for shorts or skirts to ever hit her knees.
A man who is shorter than his 14-year-old daughter.
A young woman who wears flats every day but still towers over every Tinder match.
A man who is constantly seen as the aggressor, despite his gentle nature, because he is exceptionally tall and broad with a heavy brow.
A woman who is "asked" to purchase a second airline seat because she doesn't fit in a single seat
Every one of these sentences conveys relative size but more importantly each one also conveys at least one struggle the character has because of that size.
Most, if not all, of these examples would be better served by weaving this information into the narrative naturally, rather than shoving it in up front when we first meet the character. First impressions matter, but a lot of this is better found in nuanced ways as we follow the character through their adventures.
If you don't mention any size, your audience will most likely subconsciously default to averages. Or, actually, they'll default to the averages of fictional norms. If your female character isn't described, the audience will automatically imagine someone who is white, 5'4"ish, wearing a size eight dress with a pretty face and shiny hair. If your male character isn't described, your audience will default to someone who is white and 5'10"ish with softly visible muscles and a full head of hair.
These assumptions aren't fair, of course, but they're real. If you want to offer something different to your audience, you're going to have to show why and how your character is different without resorting to hard numbers that can be interpreted ambiguously and kick your reader out of the story.